(1) The current system uses a large number of load tap switches are oil-immersed tap-changer, and its insulating medium and arc-extinguishing medium are transformer oil.

(2) Oil-immersed vacuum-loaded tap changer, which is a new technology product developed in recent years, its insulating medium is transformer oil, and the vacuum tube is used in arc extinguishing medium, so that the insulating oil of the switch oil chamber will not cause pollution, and the running cost is reduced and the reliability of power supply is improved

(3) Dry-load tap changer is divided into dry-type vacuum and air-loaded tap-changer according to its insulating medium and arc-extinguishing medium. Dry-type vacuum and air type on-load tap changer, generally for small capacity of dry-type transformer accessory products.

2. By phase number classification: divided into single-phase and three equal.

(1) Single-phase load tap switch can be used for Y or △. Each contact of the three-phase tap changer can be used as a single-phase tap-changer by direct parallel connection. Single-phase on-load tap changer is generally used in 220Kv and below large transformers or three-phase transformer combination of transformer group. 220KV and above large transformers or three-phase load tap switch, can be equipped with an electric mechanism for operation.

(2) Three-phase load tap changer has Y-junction and △ two kinds, three-phase voltage-regulating winding is connected to Y-junction by tap-changer, such tap-changer is often used for neutral point voltage regulation. The three-phase voltage-regulating winding is connected to a △ knot by a tap changer, which is often used for line-end voltage regulation or central pressure regulation.